Textile drawing process and apparatus



United States Patent TEXTILE DRAWING PROCESS AND APPARATUS Oskar Kiinig, Stuttgart-W., Germany, assignor to SKF Kugellagerfabriken G.m.b.H., Schweinfurt, Germany Application June 24, 1955, Serial No. 517,859 Claims priority, application Germany June 30, 1954 2 Claims. (Cl. 19131) The present invention relates.to a process and apparatus for drawing fiber bands composed of fibers at least half of which are essentially .of the same size.

With conventional drawing mechanisms of finish spinning machines it is practically impossible to obtain a yarn of completely uniform thickness and otherwise uniform properties. On the one hand, the purely statistical variations in the distribution of fibers produces a minimum lack of uniformity, and this lack of uniformity is present even at the pre-spinning machine, and on the other hand the lack of uniformity in the yarn is additionally increased by faulty drawing. The principal factors resulting in faulty drawing in the main drawing field of the finish spinning machine are an insufficient guiding of the floating fibers and aperiodical wandering of the nipping point of the drawing rolls back and forth in the drawing plane which may, for instance be produced by untrueness of the drawing rolls. This last factor produces periodical variations in the thickness of the yarn. The high drawing which has come into use in recent times provides an improvement in the guiding of the fibers, but at the same time the yarn defects produced by the wandering of the nipping point increases proportionally to the increase in the drawing and therefore limits the maximum drawing which can be used.

This periodical wandering of the nipping point is impossible to eliminate completely, since upper drawing rolls cannot be ground so that they are perfectly true and furthermore the coverings for these rolls cannot be given an absolutely uniform elasticity or compressibility. It is these latter two factors which cannot be completely eliminated from present day upper or lower rolls which result in the wandering of the nipping point of the drawing rolls and which thus limit the amount of the drawing, since the yarn produced by the drawing mechanism must not have less than a certain minimum uniformity. Moreover, it is often impossible to avoid the presence of individual top or bottom drawing rolls which engage the yarn with unusual force and provide a yarn of poorer than usual quality which cannot be removed from the total product with conventional controls and thus result in complaints to the mill. The abovementioned periodical wandering of the nipping point produces a lack of uniformity in the yarn, and this lack of uniformity has a cyclical variation whose cycle has approximately the same length as the circumference of the top or bottom drawing rolls.

It is an object of the present invention to overcome the above drawbacks by drawing a band of fibers in a drawing machine according to either of a pair of processes in accordance with the present invention which result in a yarn of almost uniform thickness.

It is also an object of the present invention to provide a drawing capable of producing a yarn having a far greater uniformity of thickness than yarn produced with conventional drawing mechanisms and diifering from conventional drawing mechanisms essentially by the size of particular drawing rolls.

2,930,085 Patented Mar. 29, 1960 ICC The concept of the. present invention is basedon the recognition that a band of fibers of predetermined length will have a constant thickness if the density of the fiber ends varies cyclically according to cycles each of which has a length of l/n, where l is the fiber length and n is a whole number. It is to be understood that by density of fiber ends is meant the number of leading or trailing fiber ends per unit of band length. With such a cyclical variation in the density of fiber ends the number of fibers at any given point of the drawn band of fibers is uniform. If the fibers of a given band are not all of the same length and l signifies only an average fiber length then an absolutely uniform yarn thickness cannot be obtained, but nevertheless, if a cyclical variation of fiber density according to the average fiber length is provided there will be a considerably improved uniformity in the yarn thickness. This improvement is also produced if only approximately half of the fibers of a given band are of approximately the same length. The lengths of the fibers of approximately the same length can vary from an average value by approximately The above mentioned cyclical distribution of fiber density with reference to the average fiber lengths of fiber of approximately the same length can be produced by making the circumference of one of the drawing rolls equal to the average fiber lengths divided by n, where n is a whole number, which is preferably one, so that any nipping variations occurring during onerevolution of the roll, for instance due to untrueness of this roll, will act on portions of the undrawned band of fiber which are spaced from each other a distance equal to the average fiber length or a distance equal to the fiberlength divided by a whole number.

It is evident that if the circumference of the drawing roll is made in relation to the average fiber lengthsas defined above, every fiber passing under the drawing roll will be affected by any untrueness of this roll. Since the untrueness which will produce an increased or reduced drawing will act on each and every fiber as it passes under the roll, if the circumference of the roll has the above. defined relationship to the average fiber lengths, the untrueness of the drawing roll will not produce an uneven drawing action.

If the drawing apparatus is used for drawing different fiber materials which have a different average length, it is sometimes desirable not to exchange the drawing roll when switching from drawing one material to drawing of a different material of different average fiber lengths. In this case, the circumference of the one drawing roll will not have the above defined relationship to the average lengths to the fiber to be drawn. An untrueness in this drawing roll will therefore not affect each fiber as it passes between the drawing rolls and an uneven drawing of the band will result, whereby the uneven drawings will be equally spaced along the lengths of the band a distance equal to the diameter of the drawing roll producing the unevenness. This unevenness of the drawing of the band can be compensated for by subjecting the band to a second drawing operation by an additional pair of drawing rolls. v

The apparatus for carrying out the first process mentioned above includes in accordance with the present invention a drawing roll of a pair of drawingrolls, preferably the top roll, having a circumference of approximately l/n. Although either the top or bottom rolls can have this circumference, it is particularly practical to provide the top roll with this circumference since in carrying out the drawing process non-uniformity is most frequently provided by the top roll which is usually rubber covered, while the multiple-grooved bottom roll of a conventional drawing mechanism is relatively massive and can be manufactured and supported for rotation far more accurately than the top roll. Also, the diameters of both of a pair of drawing rolls can correspond to the requirements of the present invention, but it is more practical to form only the top roll in accordance with the present invention and to make the bottom roll essentially greater in diameter. With such a larger bottom roll the cyclical variations of the density of the fiber ends is not undesirably influenced by variations produced by the bottom roll since these latter variations have a relatively long cycle and are of minor significance because of the greater accuracy in the manufacture and mounting of the bottom roll.

When the second of the above-mentioned processes according to the present invention is practiced, the apparatus for carrying out this process includes a roll ofa pair of drawing rolls, preferably the top roll, of a first drawing field, this roll having a circumference of approximately l/ p, and drawing rolls of at least a second succeeding drawing field which are so arranged that the total drawing elongation is p/g, where g is a whole number.

When the process of the present invention is used for drawing cut staple fibers or selected cotton fibers, the circumference of the smaller drawing roll will be less than 60 mm., in view of the fiber length. When drawing worsted fibers the circumference of the smaller of the pair of drawing rolls of the present invention will be less than 110 mm. in view of the fiber length.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a graph illustrating the fiber end density of a given band of fibers;

Fig. 2 is a schematic side elevational view of a first embodiment of a drawing mechanism according to the present invention;

Fig. 3 is a schematic illustration of a second embodiment of a drawing mechanism according to the present invention; and

Fig. 4 is a schematic illustration of a third embodiment of a drawing mechanism according to the present invention.

Fig. 1 shows a graph illustrating the cyclical variation of fiber end density y as a function of the fiber band length x, and Fig. 1 clearly illustrates why the cross section of a band of fibers at any point will have the same number of fibers when the fibers have the same length and where the density of the fiber ends varies cylically according to cycles having a length 1 equal to the fiber length.

The curve x=f(y) shown in Fig. 1 has a cyclical variation each cycle of which has a length l, and this length l is at the same time the length of the fibers of the band of fibers. It is thus easy to see that the number of fibers in any cross section of the band, or in other words the thickness of the band of fibers is where l is both the fiber length and the cycle length. This value of C remains the same irrespective of where the point x, is taken, and therefore the thickness of the band of fibers can in general be indicated by which is to say that the thickness of the band of fibers is at all places along the band equal to the constant C.

In the embodiment of the invention which is schematically shown in Fig. 2 a drawing mechanism capable of carrying out one process of the present invention includes a top entrance roll 10 and a bottom entrance roll 11 which together form a common nipping point 12. A bottom belt 13 extends about the bottom entrance roll 11 and is guided over the stationary bar 14. The tension in the bottom belt 13 is provided by a tensioning lever 16 turnable about the stationary pivot 15 and being urged in a clockwise direction, as viewed in Fig. 2, by the spring 17. A top belt 18 extends about the top entrance roll 16 and is guided over a cage 19.

At the discharge end of the belts is located a top drawing roll 20 and a bottom drawing roll 21 which have a common nipping point 22. A guide belt 23 extends about the top drawing roll 20 and about a delivery roll 24, and the belt 23 is so arranged that a portion of it extends along the outer surface of the bottom drawing roll 21.

The undrawn band of fibers 25 is drawn at the portion 26 thereof located between rolls 10, 11 and 20, 21, and the drawn band 27 issues from the rolls 20, 21.

One of each of the pairs of the rolls is driven and the band of fibers 25 is drawn in the drawing field located between the nipping points 12 and 22. The circumference of the top drawing roll 20 is equal to the length of the fibers in the event that all fibers have the same length, or the circumference of the roll 20 is equal to the average fiber length where the fibers have different lengths as discussed above. The circumference of the bottom drawing roll 21 is much greater than that of the top drawing roll and is a multiple of the circumference er the top drawing roll. In this way, the lack of uniformityof the bottom drawing roll is for the most part eliminated and the wandering of the nipping point 22, produced by lack of uniformity in the top drawing roll 20, is cyclical, and each wandering cycle of the nipping point 22 has a length equal to the length of the fibers if they are of the same length or equal to the average fiber length if the fibers have different lengths.

In the embodiment illustrated diagrammatically in Fig. 3 the drawing mechanism includes a top entrance roll 30 and a. bottom entrance roll 31 which produce the nipping point 32. A lower belt 33 extends about the bottom entrance roll 31 and is guided over a stationary bar 34.

The pair of drawing rolls of the embodiment of Fig. 3 includes a top drawing roll 35 and a bottom drawing roll 36 which together form the common nipping point 37. A slip roll 38 is located ahead of the drawing rolls. The band of fibers is indicated with the same reference charactors as in Fig. 2. The, top drawing roll 35 has a circumference equal to the length or average lentgh of the fibers, and thus the embodiment of Fig. 3 produces the same result as the embodiment of Fig. 2. The circumference of the bottom roll 36 is a multiple of the circumference of the top roll 35 so that the influence of lack of uniformity of the bottom roll 36 is reduced to a minimum.

Fig. 4 shows an embodiment of the invention capable of performing the above-mentioned second process according to the present invention. A top entrance roll 40 is located over a bottom entrance roll 41, and these rolls provide a common nipping point 42. A bottom belt 43 extends about the bottom roll 41 and about the stationary bar 44, and the top belt 45 extends about the top entrance roll 40 and is guided by the cage 46.

A main top drawing roll 47 is located over a main bottom drawing roll 48, and, these rolls have a common pp g p int 4,9. Between, the nipping points 42 and '49 is located the main drawing field of the drawing mechanism.

leaves the drawing mechanism of Fig. 4 as a fully-drawn I band 56.

The drawing produced by the embodiment of Fig. 4 is as follows:

First, the band 53 is drawn in the main drawing field located between the nipping points 42 and 49. The circumference of the main top drawing roll 47 is Up, where p is greater than one. I is the average length of the fibers of approximately the same length. The main bottom drawing roll 48 can have any size although it is more practical to give the bottom roll 48 a circumference which is a multiple of the circumference of the top roll 47. The wandering of the nipping point 49 resulting from lack of uniformity in the construction of the main top roll 47 produces variations in the density of the fiber ends which are cyclical, and each cycle of variations has a length of Up. In order to convert this latter cycle length into a cycle length required according to the pres-' ent invention it is necessary to draw the band 55 which leaves the rolls 47, 48 in the drawing field between the nipping points 49 and 52 with a drawing of p/g, where g is a whole number.

As a specific example of this process let it be assumed that p=l.5 so that the length of each cycle of variation of fiber end density of the fiber band 54 upon leaving the main drawing field is l/ 1.5. If g is equal to one, then the band 54 must be further drawn in the auxiliary drawing field between nipping points 49 and 52 with a drawing of useful application in other types of drawing process and 4 apparatus difiering from the types described above.

While the invention has been illustrated and described as embodied in a drawing process and apparatus for producing a yarn of uniform thickness, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully re- 5. veal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from. the

standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A process for drawing a band of fiber comprising the step of directing a band of fibers, at least half of which have substantially the same fiber lengths along a drawing plane between at least one pair of drawing rolls at least one of which has a circumference equal to said fiber lengths divided by n, where n is a whole number, whereby substantially even drawing of said band of fibers is obtained even if said one roll is untrue.

2. A process of drawing a band of fibers comprising the steps of directing a band of fibers, at least half of which have substantially the same fiber lengths along a drawing plane in desired sequence between a first pair of drawing rolls, one of which having a predetermined circumference and the other of which is considerably larger, and between a second pair of rolls causing such 1 an elongation of the band that the absolute'value of said elongation multiplied with said predetermined circumference is equal to said fiber lengths divided by n, where 1 n is a whole number, whereby substantially even drawing of said band of fiber is obtained even if said one roll of said first pair of rolls is untrue.

References Cited in the file of this patent UNITED STATES PATENTS 0 1,181,928 Schewelin May 2, 1916 1,583,893 Meier May 11, 1926 2,133,657 Devaux Oct. 18, 1938 FOREIGN PATENTS France May S, 1930 

